Fluid-pressure system.



B. AIKMAN. FLUID PRESSURE SYSTEM. APPLICATION FILED MAY 27, 1907.

Patented Nov. 3, 1908.

2 SHEETS-SHEET 1.

MNR

QUALE/4 maar I M www B. AKMAN. FLUID PRESSURE SYSTEM.

APPLIUATION FILED MAY 27, 1907.

2 SHEETS-SHEET 2.

' Patented Nov. 3,v 1908.

" no. cones?.

TooZZ whom it may concern." y Be it known that I, BERT AIKMAN, citizen ot the United States, residing et Chicago, in the county of Cook and State of Illinois, have nvented aoertein new and useful 1m roveinentjiii FluidPressure Systems, of which the following is a full, clear, concise, and exactv f description, referen-ce being hed to the ac- [coinpenying drawings, forming a port of this j Specification. f My invention relates to motor compressor A rsteins, its object being toprovide more effici nt arrangement and o eration;

\ My systeiiinbeliongs to t at class in which a compressor" for supplying. thereservoirv is drivenfh'jr an electricniotoi' with which is essociated resistance which is gradually cut out inf circuit wlienthe niotoriis started and in lwhicliivel'ves of the coinpressornre incapacif Qt'ateduntil the inotor has obtained full speed r `ors speed which it cany best take on a load. lnf son'ie'ot thcseprior systems the valves of' .thefeoinpressors, for instance, the suction jvalves were controlled to renderA the coni` ,fpressl'ii inactive until the motor assumed a suitable speed, `and y.these valves have gener-l all)P been controlled by electrical` ineens, so 'n'oidsbeingv usually employed to operate i t ievalves. 'n Electrical controlling mechani isniisfalsousedy for gradually rendering the motor 'resistono-e.ineiliective to cause gradual ystar't ofv theinoto'r."y f This. electrical control mechanism which` inadethe system nio're or less expensive ot construction, end this elecfieliable, as the windings are easilyr burned outl'e'nd the delicate neinji'liredptlie' co .hereforefver i electric current ioropcrating these ele-c2 trical mechanisms involved further expense.

kl iniproveiil"syst'ein is en tiiclv devoid of of maintenance being,

-v controlgbeing eiifected by pneumatic means.

1This makes it possible to build stronger coni it more siiiiple n chan- .pressed vair, ow'ergelectiicel operation.

Specification of Letters latent'l Application led May 2'?, 1907. Seriai No. @75,831..

` iin-volved the use of e great many electrical circuits, wini'lings, and more or less delicate tricel control furthermore is more or less unmechanism yimho-lanc-ed uisid'eiehle.- Again, the use elect cel controlling mechanisms, the entire parts "linen,

MBEiiT A'nMAN, 'or CHICAGO; fiLiiiNois, AssieNoR Tol NATIONAL BRAK'sL `ELECTRIC' IooiviPAinz, or MiLwAU'iuis, wisconsin, A CORPORATION or wisconsin.

resented Nov. iees.

described by referenceto the accompanying S5 'dreWings, in which Figure 1 shows e complete system, the operntive parts lor controlling the motor being -shown more or less diagrammaticall3T end the pneuinstic governor being shown in vertical section;- Fig. 2 shows another vertical section of the pneumatic governor; Fig. 3 is a top` view oi the low ressuie valve freine; Fig. 4 is en elevation view of the low pressure springl thirnble, and F ig. 5 is en enlarged view showing an arrangement of the suction valve controlling mechanism. l

In thesysteni es shown, the electric inotor l is coupled through suitable gearing mechanism 2 to the piston rod 3 terminating in the f piston head 4 within the compressor cylinder 5. vPipes 6 and 7 lend :from the ends of the compressor cylinder and into a iuain pipo S which feeds to the reservoir Q, thc 110W Athrough pipes G andbeing controlled by cliecli valves 10, 1l. Suction valves 12 and 13 nre valso shown through which air issupplied to the compressor. yOne terminal olE the niotoi' shown ns connected ground G, while the other terminal connects nor-l inelly through resistance sections 111, R2, 1i, 'Rf end R5 with the switch contact 14 oi' the pneumatic governor, the associated switch contact 1.5 being connected with line through a niainswitch S.

The motor controlling apparatus coniprises a inain cylinder piston outfit Mond a plurality of suh-cylinder piston outfits C1, C2, C3, I and. C5, equal -in number to the resistance sections. The niain cylinder piston out-tit comprises the cylindrical inciosing shell 16 whose upper part 17 is ot greater diai'rieter than theloweripart 1.8m provide a y ledge 19j yi'lifdeptcd to."A reciprocate iii the upper :part-*is e, piston 20 and adapted to reciprocate 4in thev lowerr )art is a piston 21, these pistons being united b v the cylindrical shell 22. Within this' shell is pocleted a spring 23 4which ahuts against the o'istoii 20 andthe ahutincnt sto 24 threaded into the lowerwsll of the cylin( er traine. Extending upwardly troni theupperpist'on arer the4 arms 9 f tlieD v'alve whifclirests on the V2J,fthe"noi-mal)position of the, tioned beingshown, the coinend reliable operation. oicoin- My inventionwill'be best understood when pression springr holding tliepiston trames up` with `the valve 'against the stop 28 at the u i per end of the velve seat. vLeading from t e ics upper end of the valve sent cre the ports p1, p2, p3, p4 and pf connected, respectively', with the sub-cylinder piston outfits C1, C2, C3, C* sind C5 es shown. he port a also leads from the valve seat to atmosp 1ere, and the port pe leeds through ipe 29 to the cylinders 30 and 31. in the'cyhnder 30 isa, piston 32, While in the cylinder 31 is n. piston 33. Between the piston 32 and the intermediate Well 34 in cylinder 30 is the compression spring` 35, While in cylinder 31 between the piston 33 and the internuuliate Well 36 is e compression spring 37. The stems 12', 13 extend from suction valves 12, y13, respectively, and through the Walls 34 and 36 to he engaged by pistons 32 and 33 when the `ressure reaches nc'erteinpoint. Collersli and 35 on the stems limitthe movement .of the valves. Gpenings 36 and 37 in cylinders 30 and 31 communicate with the suction valve chambers. A pipe 38 connects the upper compartment 17 of the mein cylinder With theireservoir.

Cylinder pisten outfit C1 comprises the cylinder o1 and the piston '7J/ rthe piston rod 'r1 terminates in e Contact arm atdepted when the piston is moved out to connect together contacts w1, y1, which contacts are bridged about theI resistance section R1. Between the piston h1 and the cylinder head is :t compression spring,` s1.

Cylinder piston outfits C, C, C* and C5 have the suine parts es outfit Cl, but the reference chr-.meters nrev given subscripts 2, 3, 4 und 5, respectively. lThe contacts 1r?, e, zr* and ere ell connected lin common with the entrence terminal o'r' the resistance through conductor 39. fore sta-ted, is connected with the end of resistance section l. Terminal if* conn'cts with the end of resistance section R2 contact y connects With the end of resistance section R3; contact y". connects with the end of resistance section R4, and contact if connects directly with the motor terminal. In the normal position the sub-cylinders are connectcd with atmosphere througlrtheir respective port openings through the D vulve and through atmosphere port pa.. lVhen the piston trame within the main cylind r is driven downwardly, port p1 is iirstdiscon nected 'from atn'uisphere and exposed to receive nir under pressure fed to the main cylinder from the reservoir through pipe 33, and outfit t" is actuated to close contacts r1, y1, thereby short-circuiting resistance section l. li'ort ya next exposed, and outfit (J2 is :u-tneted to short circuit resistance section lig, and so onports p, p" and p5 are successii v"`ex,iose l, to successively short-circuit sections lt, lt" and lt, when the entire resistance will he rendered inoilective und the motor connected directly with the 'pneumatic lgovernor switch contat 14,

The distancel between atmospheric port Contact y1, as heel pm and port pe' is such that after the ports p1 to pf have heen successively exposed, the D valve will spun the ports pa, po in order to connect the suction valve cylinders 30 end 31 with' atmosphere. The springs 35 und 3 7 in the suction valve cylinders are adjusted to, say, about. twenty' pounds so that they will not allow movement et the pistons 32 und 33 to inluence the suction valves until the pressure on the pistons a iroaohes twenty pounds per square incn. vhe spring 23 lfor the main piston trame hns :t comparative adjustment of about 'tive pounds, that is, it will start to move when the pressure becomes about live pounds per square inch and so that the upper piston '20 will reach the ledge 19 when the pressure gets to he about eight or ten pounds. With this arra'tngement, when the motor is started with the pressure in the reservoir at Zero, for instance, the suction valves ol the compressor will he operative -end air will be comypressed in the reservoir and this compressed air reaches the cylinder above the piston 2() through pipe 38. The piston frame is moved dmvntverdly sind the vulve carried therewith to gredually expose th(` port openings to the pressure, und' the piston 20 will reach the bottom of its stroke' before the pressure will have any effect on the suction vulve springs and, therefore, the compressor action Will not he e'ected, hut, as before stated, when the Valve reaches its lower position, the ports po ends/1e are connected together Which means that the cylinders 30 :md 31 ere connected with :'itinosphere and the suction vulves are then ,entirely free from the Vel'ects et pressure and the .motor can operate the compressor in a normal manner.

l shell now 4describe thcpneumatic governor mechanism for. controlling the operation ol the main piston Vl'rame when a certain maximum and mininuim pressure are reached in the pressure system. ln generil, the operation issuch that the lower compartment 18 of the main pistou outfit is connected with atmosphere when the` pressure reaches minimum or is beloof minimum, und connected with the reservoir when the pressure reaches maximum, the pr ssure being equelized to the reservoir pressure at hoth sides of the piston 20. Spring 23, of course, will become eil'ectivc to 'raise the piston frame and to gradually reinclude the resistance sections in circuit to gradually reduce the speed of the motor, the operation of the pneumatic cgovernor heine' such that when this resistance is rcincluded in circuit, the feed line to the motor will "ne broken at contacts Hund l5. i

As l do not desire to claim the mechanical constructioii und arrangement of the pneumatic Agovernor mechanism, l have shou'n just enough. thereoi' to illustrate the operaile l tion of f tion with t sorteer e remainder ofw'the system.

' The governor comprises 'the base part 40, the sub-base part 411 and the cover 42. .ln Fig. 1 the governor i's shown in section taken on a Vertical plane passing through the line connecting the 'centers of the low pressure `:Valve compartment 43 and the high pressure piston compartment 45.`

valve compartment 44, while in Fig. 2 the' governor is shown in sectional View taken on a vertical plane passing through the line connecting the centers of the high pressure vulve compartment 44 and the contact mecl'ianism .These valve compartments areall' in the base part 40. 1n

l the sub-'base part` 41 is the pocket 4G for re- ,'the-d'iaphriigm to the'ledgc 5G.

ceiving the compression spring 47 whose lower end engages the top 'of' the thunble 48 'thimble has the legs 49 and 50 which straddlel over the cross bar 51 ventr-ruling across the central opening' 52 of the cylindrical low pressure valve `frame 53, the diameter of the cylindrical thimhle heilig less than the diameter of this opening. rThe legs 49 and 50 engage the Valve' button 54 which engages `the diaphragm 55 suprmrted on the ledge 56 This plarts and the operation in connec-y forming the i'loor ot the valve chamber 4B.,

The lowpressurevelve frame o3 hns the up'- per lla-nge 57, shown screw-threaded into the ripper end of the valve compartment 43,

and the lower end 5S ot' the valve tru-'me hears against the diaphragm to clamp Athc-edge ol' downwardly from the center ot'the cross har '5l 1s the hub 59 forming a guidewayl'or the '.yalve stem 60 extending l rom the vulve hut- ,ton 54, and the lower inner edge 61 of the huh islhev'e'led to form a valve seat for the conical part 62 between the valve stem and tlrehut ton. The djustment is such that when the diaphragm is normell)Y held down by the torce ot the spring 47, the valve cone will be away from the seat to allow communication :between the Valve chamber G3 und the passageway'64 extending dimm-itrically across 'the valve traine. 53 through the cross har 51, this passageway communicating at its ends with the compartment 43. When the die- `phragm is up, the valve cone will engage the seat 6i, and'communication between charnhers 43 and o3 will he closed. The spring 47 is of such dimension that it will allow the. diaphragm to raise when the pressure reaches the determined minimum value which in Extending 4practice may be about 'sixty pounds. An ed justing screw is shown for adjusting the action of the sprlng47v` The high pressure Valve 6G has the 'piston "l [lientlfg' `reciprocal.--witlrin the` 'compartment Y s ein' 68 of the valve engages in the `v'valvechannel and the vupper ed fe 70 `ol' l this channel `is beveled to i'orm a valve seat vThe;

to `he enga-ged by the conical section 7 l on the Valve stein. "'l`hev diameter o' the Valve so thatthe normal actuation surface of the `valve is equal to the sectional area ol the space between the valve stem and channel.

The lower part ol' the head 67 is also cutaway y at the hase of the conical part7 l to allow lor the annular chamber 72, this annular chamher being vconnected with the compartment 43 of the low pressure valve through .the passageway 73. A passageway 74 connects the valve channelt) withA the compartment 75 helow the diaphragm, and this passageway communicates through pipe-76 with the res-r ervoir. -The valve stein ishollow to form a pocket 77 fory receiving the lower end ol' compression spring 7S whose'upper end extendsvinto the pocket 79 cast int 1e subeoase part 4l.

This spring which normally holds the high pressure valve upon lts seat, 1s ad- ]usted to respond only when the pressure reaches the maximum value.A Connecting the pockets 79 and 46 is the passageway S() which passageway connects with atmosphere through the port 8l which is of comparatively small diameter. A screw 82 is shown hy means ol' which `the 'adjustment ol' the spring 78 may be varied. The compartment 43 for the low pressure valve mechanism conA nects through pipe S3 with the main cylinder 16 et a point bellow the piston 20. c

in the piston compartment 45 is the piston 84 Yfrom which extends they tubular piston rod E45 guided at its upper ei-i-dhy thellange Sont the upper end otl the shell orlranie S7 tl'irough which the piston passes, thisrrshell forming part of the sub-hase 4i. rVifithin thisV shell S7 and the piston compartment is the compres# sion spring 8S shutting .against the piston and the flange SG, this spring serving norH inallv to. hold the piston down against its :tnnul'ar seat 8S). Secured to .the upper end oi' the tubular piston rod is the contact frame Q() which at its iront end carries contacts 9i and 92 connected by conductor 93. Extending rearwardhv from the Contact `l'ran'ie are the guide hearings Q4, 95 engaging the guide-rods 9G and Q7 suitahl)T supported from the suhhase l'raine. As the piston 84 is raised, the contact l'rame is also raised to disconnect contacts lll, 92 from contacts i4 and l5, and

when the piston is returned, the contacts are4 V:conipnrtment 44 with the compartment QG" formed below the piston 84 when kthe piston Yis down, the conneetionbe'ing through a re stricted port opening 167. The sides et the piston chamber `45 andthe seat 89 are; also iso .dak

slotted to forni hy-piisses S. Through the wel] of the piston 85 is .fui inletopeiiug 109 sind at the upperfend thereof opposite the engaging-@mis o f the eoritiipt itieinhers nre the outlet openiiigs 110, 111 sirriiiiged ro direct'I i ooinpressed zur to hlow out fires formed upon g erste and air is immediately conipressed into the reservoir, und this pressure is distrihuted from the mitin reservoir through the pipe 76 to the passageway 74 under the high mid low pressure valves end also to the main pistonfeylindi-ir shove tliepiston 2() through the pipe 3S. The springsol' t ielow und high pressure Valves, however, are adjusted nt, sfiy, sixty and eighty pounds, respertively, and the suction valve springs nt twenty pounds and will-nothe nileeted iniiiiedintely. The mein piston. spring 23, however, is of low adjustment, sis already inentioneih :ind will sto/rt to more when the pressure. `gets to he aboutl tive pounds to the square muh, nud when lthe pressure hns reached, sii-y, shout eight or ten pounds to the square inch, the

piston 2t) will he in its lowermostl position against the ledge 19. rlhe eompzirtment helow the piston 20, :is is understood, is nor1 iniilly eonneeted with atmosphere through pipe S3, compartment Ll?, 'passageway 61, compartii'ient 63, passageway S() and through port 81. 'lhe piston 2t) will, therefore, rezieh its'lowr-irniost position he tore the pressure heeomes high enough to nrll'eot'- the operation of the suction valves in the eompressor and during the downwiird movement of the D vulve /26 which is carried with the piston, is .fil-

-vwith the line.

ready described, the Various suh-eoiitnet out;- tits G1 to t1; will he successively renner-ted with the reservoir to successively eut out of Cireuit the resistzinee seetions ll1 to R5 to thus griiduailly i-,olmeot the motor direetly Also, :is lu s iilreaidy heen described, the D vulve :it the end of its stroke connects pipe port 'pr with :it'mospherie pori' pa, :ind thus the suction "nire cilinders Slt), 31 nre eonneetzed with atmosphere und the operntion of the suction vulves is zihsoiuteliv unhiiidered hy :my :tir pressure, und the motor run (outinue driving' the compressor il at its full rnpnf ity to dui; lily bring' the pressure iii the reservoir up to normnl. As soon es the pressure reiizvhes the minimum pressure Value which hns heen ussunied :is sixty i pounds, the die phrngni supporting the low pressure vulve hutten will he raised to curry the' coiiiriil pnrt (i2 oi the vulve against the Valve sent'y (31, thus to elose Communication between passageway Gul and Qompnitment 46 connected with atmosphere through passagewey St) find port S1. 'li'his ineens that the mein cylinder below the piston 2t) is disconnected from. atmosphere :is well as comparti ment 106 helow the rontoet piston S4 and vroiiipzirtment 72 under the high pressure volvo piston 67, this compartment 72 bein;Y (-.onneeted with passageway 6l through port T3 und eonipzirtinent 106 being connected with eoiiipnrtnient 72 through 'port 107 :ind pzissngewny 105, shown in Fig. 2.

Now when the pressure reaches the maxi-- .inu'ui pressure value or eighty pounds, the

high `pressure vulve will he rnised to allow eoniieetion het-weon passageway 74 find compartment through the eouiportniei'it Il, :ind the reservoir, t|ieretore,

72 und port i will he mime-stedwith the eliiiiiiher below the moin piston 2t) sind also with rompertment 10G helow the Contact piston hy wey of pzissiijrewuy 105 :ind port 107. Owing to the hy-pnss shout piston S4 :indthe restrietei'l dinnieterpf the port 107, the operation el the piston S1 will he gradual. 'the pressure :it hoih sides ol' piston 2t) being suddei'ily eqiuilized, spring' 23 heroines .ei'l`eetiye to restore the piston und the D vulve hurried therehy to' their normal position. The movements ol' this piston frame nre also more or less grriiduul on zieeount of a Cheek vulve 1.119 carried hy lower piston 2]., which valve when oli Aits sont exposes large hy-piiss 110 through the piston, hut which when on its seat restricts ythe hy-pnss to the simili opening 111 through the valve, the hottoiii ol the -Cylinder heilig Vlilled with. oil. The upward movement oi the piston frame lis therefore inoierzipid than the downward The 'first e'leet upon upward movement of the D vulve Iwill he to disconnect port pv from atmosphere n-iid to releiiso this port so thiit :iir under reservoir pressure muy enter through pipe 2t) into suction vulve cylinders SO und 25| to roiso pistons 32 :ind $321 zigninst the pressure ol springs l?) zuid 117 und :igrfiiiist the vulve stems, therehy raising' the. suction ri Ives oil' their seuls to iurzipiii'itute the fomi pres-sor. Upon further upwzird movement ol' the D unive to 'its noi-mul position. the

surressively ilisc'onerted| [from reservoir pressure und 'eonnerted with ntniosidiere so thutl their pistouszire restored :ind their rontoets disronueried to euse the 'resistor -e sertions it", Pi. ltf. ll" :mdlt to he sucressireli' reiiirluded in the motor eireuit, :ind the motor thus ,ujrz'idmill'i' slowed down. ily the time. this hns heen zieeomplished, Sulli-` rieut pressure will hnve pnssed through port Y 902,637 l A u? and against the .piston 1%, to throw this piston upwardly against J the'pressure of the Ispring- (whichisadjusted to about twentye I 'live pounds), and contacts 91, 92 will be dislaengaged-and contacts 14 and 15 will brealg `the motor circuit. Compressed air may enter through by-passe's 108 to the compartabout sixty pounds as assumed, the suction valve springs will remain overcome andthe sucton valves maintained ine-Elective and the alreedy been described, and suction valve cylinders 30, Sl will be relieved and the suction valves rendered eilective.` The com 75 l inentsabove thepistonand into the hollow, `piston ro'dopening 112 and from thence out* 10 wardly through openings 113 and 1141 tov `brought into engagement.

f c5 voir being at minimum pressure value or a blow out any arcs-which might occur as the contacts are disconnected. When the piston 84 reaches the top vof its stroke, connection between byepasses 108 and the interior oli the is` piston rod will be shut oil. Thus, the motor and the compressor are gradually started and gradually disconnected.

As has beenexplained, valve 66 at the startoiers a restricted area. As soon, however,

y2o as it leaves its seat under eighty pounds pressure, a much greater surface is offered and 'much less pressure, (about forty) is requisite to complete its movement and to hold it, and therefore'as long as the pressure remains v:25 above the minimum value, the above condit'ion of affairs will be maintained, but if the pressure' should drop below sixty poinds, springe? becomes etiective to push the low pressure valve downwardly to vagain estab- 1 F30 lish communication between compartments 43 and 63, thereby reconnecting the compartment below the main piston 20 with atmospherc and also connecting with reservoir the compartment 7 Q-above the high pressure valve piston 67, and the pressure becoming thus equalizodat both sides of the high pressure valve, this valve is returned to normal by s ring 78. The .restrictedby-pass 8l. will not iind-er this edualizing operation. valve 66 reseatsthe compartment below piston 84is disconnected from reservoir and reconiiected witli.,:v atmosphere through compartment 72, port. 73,valve 62 and port Sl. Spring l855 becomes effective to restore piston 84 to its lower position and to carr. contacts v91 and. 92 again into engagement with contacts lll and 15 to'close the motor circuit. As soon piston 84 starts to move downwarllly. ley-passes lOSl'beconie el'ective and assist the port 81 inpgiving quick relief to atmosphere so that the contacts are quickly Partly on account of port 81 which is ol restricted diameternnd which Oilers the only outlet to atmosphere from below tho main piston 20, aiul partly on account of the restricted by-passA in piston 2l, thc-downward inoveiucntol" this I e motor Vto gradually assume lull power, pneu-l piston' is retarded, there being no response of the resistancefcontrolling outiits C1 to C" untiltlic governor contacts have been closed,

`anl then l'liesefrcsistance adjustiugvoutii'ts are successively" (,:onnectcd into service to successively render the resistancesections lt to 'lt5` ine-ectiye. The pi I`surelin the reserl/Vhen A piessor, therefore, will be operated to restore ,the' pressure in the reservoir, first to minimum pressure value to operate the low pressure valve withits consequent results, andthen to maximum pressurevalue to operate the high pressure value with its consequent results already described, this cycle of operations being repeated. AThe oy-passes 108 serve also to prevent accumulation of pressure in passageway 105 and below piston 84 if at any time the high pressure valve should lealnthe leakage airfinding its Way to at mosphere through' the by-passes, through vhollow piston rod 85 and out through the blow-out openings 1 i 0-1 1 1. Thus, any false operations of piston 84, and opening of the motor circuit, is prevented.

Having thus described my invention, I desire to secure the following claims by `Letters Patent: u Y 1. In a iiuid pressure system, the combination of a compressor 'for supplying the system, an electric motor for driving the eompresser, aresistance for the motor, a plurality of pneumatic mechanisms for con trolling the connection of the resistance in" l circuit, master pneumatic means controlled by the pressure in the system to cause operation of the pneumatic mechanisms to gradually change the el'lect of the resistance to cause the motorto be gradually brought to full power, and additional pneumatic means also controlled- 'by the master pneumatic mechanism for causing the compressor to be ineffective until the motor has assumed full ower and to then'pause the compressor to liecome effective to supply fluid under pressure to the system.4

2, In a fluid pressure system, the combination oi a compressor, a motor for driving the compresserf resistance, va plurality of subpneum'alic mechanisms associated with the insistance, and a niastcrfpneumatic mechanism controlled by the pressure of the system to cause operation of theA sub-pneumatic mechanisms lo cause connection of theresistance with the motor circuit tocause the y the master pneumatic ,mechanism to atleet the valves to .cause the compressor to become effective after the lmotor has assumed full power.

3. In a motor compressor system, the combination oit' a compressor, a driving motor therefor, a resistance for the motor circuit, a plurality ot' sub-pneumatic mechanisms, each associated With a section of said resistance, a

master pneumatic mechanism controlled by the pressure of the system to cause the subpneumatic mechanisms to be successively operated to associate the resistance sections successively with the motor circuit to cause compressor mechanism to become eliectire to supply l'luid to the system when driven by the motor, and additional governor valrc mechanism operated when the pressure reaches a certain maximum value to ccnnect f the pneumatic mechanism with the system to cause the compressor mechanism to be rendered incllective. v A

5. ln a luid pressure system, the combination of a compressor for supplying the system, a motor for driving the compressor, pneumatic mechanism controlling the'efl'ective operation'of the compressor, vvalve mechanism controlling the connection ofthe pneumatic mechanism with the' system, a piston for operating the valve mechanism, governor 'Valve mechanism controlled by the pressure of the system for governing the pressure on the piston, said governor mechanism being operated when the pressure reaches a certain maximumyalue to control'tlie pressure conditions on the piston to move the yalve to cause connection of the pneumatic nicch- .anism with the system to be operated to render the compressor ineffective, said governor mechanism being operated when the pressure falls to a certain minimum value to change the pressure conditions oi the piston to cause actuation of 'the valve mechanism, thereby to connecttlawpumatic mechanism vwith the system to causrl pei-ation thereolto render the compressor effective to restore thc ressurc.

6; In a iluid'pressuic system, tie coni-' bination otv a compressor for supplying ythe system, an electric motor for driving the rality of pneumatic mechanisms for controlling the connection of the resistancewith the circuit, a main valve controlled by the fluid in the system and controlling` the connection of the pneumatic mechanisms with the fluid in the system, controlling valves for the compressor, pneumatic means associated With said valves and controlled bythe main valve mechanism, said main valve mechanism being actuated when a minimum pressure in the system is reached to connect the pneumatic mechanisms for service and to disconnect lthe Valve controlling pneumatic mechanism from service whereby the-compresser is operated, said main valve incohanism being actuated when a maximum lthe pneumatic mechanisms to become inoperative, and the Valve controlling mechanism to become operative, whereby said coinpressor is rendered ineffective.

7. ln a i'luid pressure system, the com- 'bination of a compressor for supplying the system, an electric motor for driving the com ressor, a plurality ol' sub-pneumatic mec anisms, a resistance tor the motor circuit controlled by said sub--pncum atie mechanisms, a main Valve for controlling the operation of the sub-pneumatic mechanisms, controlling valves for the compressor, pneumatic means associated with said controlling valves and controlled by the main valve, said main .valve being' actuated when a minimum pressure in the system is reached to first connect thc sub-pneumatic mechanisms tor service to control the resistance to cause operation otl the motor, and then to control the valve pneumatic mechanism to allow the controlling valves to become effective, the

inuin pressure in the system is `reached to control vthe Valve pneumatic mechanism to thc sub-pneumatic. mechanisms to affect the resistance to stop' the operation ci the motor.

S. 4lu a iluid pressure system, the combination ot a compressor for supplying the system, :in electric motor'for driving the compressor, a resistance for the motor, a plurality ol sub-pneumatic contact mechanismsy connected with said resistance, a main valve,

l l i i controlling valves for the compressor, pneumatic mechanism for controlling said Valves connected with the main Valve, maximum pressure in the system causing' said main Valve to be disposed toconncct the sub-pneumatic mechanisms with atmosphere and said valve controlliiu;I pneumatic mechanism with the 'lluid under pressure iu the system whereby said resistance is ciieeti've and the compressor `valves ineilective, and manimuni pressure vin the system causing said I main valve to be actuated to gradually cencompressor, a resistance tor the motor, a plul neet the sub-pneumatic contact mechan- 'piessure in the system is reached to cause` main valve being actuated when a maxircndcr the Valves incilectivo and to control' ii o metio means with atmosphere whereby the isms With the Huid whereby the resistance 'is In w-itness whereof; I hereunto subscribe disconnected from the motor circuit and to y myname this 18th dayof May A. D., 1907. nally connect the Valveeontrolling pneu- BERT AIKMAN compressor valves are rendered effective and y Witnesses: the `oogpressor operated to` restore pressure CHARLES .J..SCHM1DT, to the syst-em. LEONARD W. NOVANDER. 

